1. Field of the Invention
The present invention relates to the field of digital data transmission with frames and relates more particularly to the retrieval of synchronization at reception.
2. Description of the Prior Art
When a digital data transmission, more especially a binary transmission, is carried out in blocks organized into words and frames, it is necessary at reception to retrieve the synchronization so as to be able to correctly cut up the flow of information received to retrieve the words and the frames. This is usually achieved by recognizing a synchronization word, that is to say a predefined assembly of synchronization bits, placed at a given position in the frame, generally at the beginning. The problem consists in recognizing this synchronization word in the flow of data received.
For this purpose, it is known to use a memory, in general of the PROM type. The advantages of such a solution are, first of all, that the synchronization words are sometimes long (of the order of 10 bits or so or even more) and recognizing them by means of a logic circuit of the combinative type is very complex. Also, this solution has a greater flexibility with respect to possible modifications than wired logic. The disadvantage is of a technological kind: the PROM memories available commerically at the present time are not sufficiently rapid for recognizing the synchronization in real time for high speed transmission networks, for example greater than 100M bits/second, particularly networks using optical fibers.
An object of the present invention is a synchronization device adapted to the high data rate, using a memory for recognizing the synchronization signal as a whole and a logic circuit providing accelerated preacquisition of the synchronization, over a reduced number of bits of the synchronization signal.